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A076055
Composite numbers which when read backwards are primes.
5
14, 16, 20, 30, 32, 34, 35, 38, 50, 70, 74, 76, 91, 92, 95, 98, 104, 106, 110, 112, 118, 119, 124, 125, 128, 130, 133, 134, 136, 140, 142, 145, 146, 152, 160, 164, 166, 170, 172, 175, 182, 188, 194, 196, 200, 300, 301, 305, 310, 316, 320, 322, 325, 328, 332
OFFSET
1,1
COMMENTS
If m is a term, then 10*m is another term. - Bernard Schott, Nov 20 2021
LINKS
MATHEMATICA
Rev[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[332], !PrimeQ[#] && PrimeQ[Rev[#]]&] (* Jayanta Basu, May 01 2013 *)
PROG
(Python)
from sympy import isprime
def ok(n): return not isprime(n) and isprime(int(str(n)[::-1]))
print([k for k in range(333) if ok(k)]) # Michael S. Branicky, Nov 20 2021
CROSSREFS
Cf. A076056.
Intersection of A002808 and A095179.
Sequence in context: A217707 A176686 A007935 * A068653 A225193 A102616
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Oct 04 2002
EXTENSIONS
Corrected and extended by Sascha Kurz, Jan 20 2003
STATUS
approved